Donate Menu

Sea of Japan Spotted Seals and Global Warming

February 1, 2008
Volume 6 | Issue 2
Article ID 2672
Sea of Japan Spotted Seals and Global Warming

Narayama Masatoshi and Fukasawa Hiroshi

In a boon for tourism, record numbers of spotted seals have appeared along the Sea of Japan coast of Hokkaido. Visitors are flocking to the areas to shoot pictures of the popular sea mammals affectionately known as goma-chan.

Spotted seals take a break in Yagishirito off Hokkaido

Those in the fisheries industry are also eager to shoot the cute, furry animals--with guns.

"For now, we cannot tolerate them just because they are cute," said an official of the Yagishiri fisheries cooperative in Haboro. "We hope we will find a way to peacefully co-exist with them."

The problem is the seal's voracious appetite. A single spotted seal is said to eat around 5 kilograms of seafood a day. And given the mammals' growing numbers, their eating habits could devastate the livelihoods of fishermen in the area.

The seals traditionally come to the Hokkaido coasts in autumn and leave for northern waters in spring. It is unclear why the seal population has soared in recent years, but observers suspect decreasing ice floes caused by global warming are the reason. One day in February, about 400 spotted seals were basking in the sun on a gymnasium-sized reef on the east coast of Yagishirito island in Haboro.

According to Kono Yasuo, a 42-year-old ranch worker in the area, the number of seals he counts per day has steadily increased to around 400 in recent years. Kono has observed the population of seals on the island for the past six years. He said the maximum number was 274 in 2003 and 2004. On Dec. 24 last year, he counted a record 557 seals on the reef. Kono said the reef is usually most crowded in December and January. Male adults and pregnant females head for the ocean in February, return to Yagishirito once, and then gradually disappear when spring approaches, he added.

Observers said the spotted seals give birth on ice floes in March and April and spend the summer in oceans around Sakhalin Island to the north. They move south again in autumn. Most of the seals had previously remained in the Sea of Okhotsk during winter, but in recent years, they have increasingly spent their winters on Hokkaido coasts, they said.

Spotted seal habitat

"Yagishiri probably offers them a comfortable stay with abundant food," Kono said. "But it will remain a mystery why they have advanced to the Sea of Japan unless changing conditions in the northern oceans are fully understood."

Increasing seal numbers have also been reported at other seal-watching spots, including the Bakkai port in Wakkanai and Rebunto island. The Marine Wildlife Center of Japan, an Abashiri-based nonprofit research organization, counted the number of seals at 25 spots in Hokkaido in February and March. The center said seal populations have risen at most of the sites.

Kobayashi Mari, a board member of the NPO and lecturer at Tokyo University of Agriculture, suggested that warmer waters may be behind the migration. "Diminishing ice floes in northern oceans have made it easier for seals to move far southward through the Soya Strait and reach the Sea of Japan," she said.

Although seals are important sources of tourism revenue for coastal areas of Hokkaido, they consume large amounts of sea products, including cod, flatfish, salmon, herring and octopus. They also often damage fixed fishing nets and gill nets.

In 2004 and 2005, the fisheries cooperative in Rausu, which faces the Sea of Okhotsk, applied for the Hokkaido government's permission to kill a certain number of seals. The fisheries cooperative in Yagishirito island and the town of Shimamaki, both facing the Sea of Japan, applied for permission to cull the animals starting in 2006 and 2007, respectively.

But hunting may not be enough to reduce the seals' numbers. "They are very cautious and jump into the ocean when they hear gunfire, making it difficult for us to hunt effectively," said the Yagishiri fisheries cooperative official.

Kobayashi of the wildlife center acknowledged that seals are not eagerly hunted these days, and that ice floes, where small fish eaten by the seals are usually found, are disappearing. "Increasingly harsh competition for resting spaces on ice and for food may further increase the number of seals (that come south to the Sea of Japan)," she said.

This article appeared in the International Herald Tribune/Asahi Shinbun on February 22, 2008 and at Japan Focus on February 22, 2008.